This invention relates to a cylinder and piston assembly.
Automotive manufacturers generally test vehicle components, such as a vehicle door, by simulating the operating conditions of the vehicle component. For example, to test the functioning of a door, the manufacturer may repeatedly open and close the door to test wear and tear. Frequently, this action is performed by a piston and cylinder, which opens and closes the door.
The cylinder is connected to an air compressor while the piston is connected by a rod to the test component. Air to the piston and cylinder is controlled by a computer. The computer directs air from the compressor to one side of the piston to move the piston and rod in one direction. When the piston has moved to one side of the cylinder, the computer then directs air to the opposite side of the piston to thereby move the piston and rod in the other direction. This cycle is repeated.
The task performed by the piston and cylinder is simple. However, a computer is still used to control the assembly""s operation. The computer adds significant expense to the testing of the component. A need therefore exists for a piston and cylinder that cycles without a computer.
The invention comprises a piston and cylinder assembly. Like existing designs, the invention has a piston that is slideably received in a chamber of the cylinder. On one side of the piston is one air inlet while on the other side of the piston is a second air inlet. In contrast to conventional assemblies, the invention has an actuator within the chamber that is moveable between a first position and a second position. In the first position, the actuator opens the first inlet and closes the second. In the second position, the actuator closes the first inlet and opens the second.
The actuator is coupled to the piston, which drives the actuator between the first position and the second position. Accordingly, air entering the cylinder on the first side of the piston expands the piston and thereby moves the actuator to close the first inlet and open the second inlet. Air in the second inlet is then allowed to expand the piston and move the actuator so as to close the second inlet and again permit air through the first inlet. In this way, the inventive assembly cycles without the need of a computer.
The actuator may comprise a body in the chamber of the cylinder. The body may move in one direction towards the first position and in another direction towards the second position. The piston is arranged to impart its momentum to the body in either direction. In this way, the body moves between the first position and the second position.
The actuator may further have a first portion and a second portion. The piston may be supported to move between the first portion and the second portion alternatingly in one direction and the other direction. The actuator thereby imparts its momentum to either the first portion or the second portion. The first portion may close the first inlet in the second position while the second portion closes the second inlet in the first position.
The invention further has a retaining feature that holds the actuator in either the first position or the second position until a predetermined amount of momentum is received by the actuator. This feature may comprise a magnet. In this way, the actuator stays in its position until sufficient momentum is imparted by the piston. This feature thereby avoids movement of the actuator with the piston until sufficient momentum has been received by the actuator to move between positions.
Another version of the invention uses a different actuator. The actuator has a member that is rotated by the piston between a first position and a second position. The rotating actuator has a first portion and a second portion. The first portion has a first opening that permits air from the first inlet into the chamber while the second portion has a second opening that permits air from the second inlet into the chamber. When the piston has reached a certain position on the member, the member rotates to close the first inlet and open the second inlet. The member is then subsequently rotated by the piston to close the second inlet when the first inlet is opened.
The piston slides relative to this rotating actuator. The actuator has a cam that is selectively in contact with the piston. The action of the piston on the cam rotates the actuator between the first position and the second position. The piston may further be mounted to a groove on the actuator. The cam may be part of the groove.
Both features permit the inventive assembly to cycle by itself. There is no need for a computer to control air flow into the piston chamber. The invention is therefore much cheaper to produce.